A theoretical investigation of the interaction between fluorinated dimethyl ethers and molecular chlorine

Halogen bonds have received a great deal of attention in recent years. In this work, the interaction between fluorinated dimethyl ethers (n(F) = 0-4) and molecular chlorine has been investigated by the theoretical methods. The two molecules are bonded together by an O center dot center dot center dot Cl-Cl halogen bond and the interaction energies calculated at the MP2/aug-cc-pVDZ level range between -15.5 (n(F) = 0) and -6.1 (n(F) = 4) kJ mol(-1). The correlations between interaction energies and proton affinity or ionisation potential of the ethers are discussed. The interaction between the molecules results in a small contraction of the CH bond of ethers and an elongation of the Cl-Cl bond. The data are analysed by a natural bond orbital analysis carried out at the wB97XD/6-311++G(d,p) level. The charge transfer from the ethers to Cl-2 is weak, ranges between 0.044 and 0.008 e and occurs mainly to the external Cl atom. The elongation of the Cl-Cl bond is related to the occupation of the sigma(*)(Cl-Cl) orbital and to the intermolecular hyperconjugation interaction between LP(O) and sigma(*)(Cl-Cl) orbitals. The interaction between the ethers and chlorine induces an enhancement of the infrared intensity and Raman scattering activity of the nu(Cl-Cl) vibration.